Double blinding with a new placebo needle: a validation study on participant blinding

Abstract

Background: A no-touch control needle in which the needle tip cannot reach the skin has been designed, and has been validated for practitioner blinding in a previous study but not for participant blinding.

Objective: To test whether the no-touch control needle can effectively blind subjects.

Methods: An acupuncturist applied, in turn, a no-touch control, skin-touch placebo and penetrating needle in one forearm of 80 healthy subjects. After removing each needle, the subjects were asked to judge the type of needle and rate the sensation of skin penetration/penetration-like or skin pressure/pressure-like pain on a 100 mm visual analogue scale.

Results: The subjects correctly identified 67% of needles overall. 17 of the 80 no-touch control needles were judged as skin-touch, and one as penetrating. In addition, six skin-touch placebo needles, and no penetrating needles, were judged as no-touch. Half of the 80 skin-touch placebo needles and 65 of the 80 penetrating needles and two no-touch control needles elicited pain. Of 240 needles, the practitioner identified 120 correctly that did not fit the probability of 1/3 (χ(2)=30.00, p<0.01).

Conclusions: The no-touch control needles may be used as a blind control for the acupuncture procedure, or to test the physiological effect of the skin-touch needles, but are not suitable for double-blind testing of the needle effect.